1. Field of the Invention
The present invention relates to a method of driving a plasma display panel (hereinafter, also referred to as xe2x80x9cPDPxe2x80x9d), and more particularly to a technique in using a round waveform for driving the PDP to reduce an application time of the round waveform.
2. Description of the Background Art
Various studies have been made on a PDP as a thin-type television and a display monitor. Among the PDPs, there is a surface discharge AC-type PDP as one of AC-type PDPs having a memory function.
(Structure of PDP)
FIG. 17 is a perspective view showing an AC-type PDP 101 in the background art. The PDP of this structure is disclosed in Japanese Patent Application Laid Open Gazette Nos. 7-140922 and 7-287548.
The PDP 101 comprises a front glass substrate 102 as a display surface and a rear glass substrate 103 opposed to the front glass substrate 102 with a discharge space 111 sandwiched therebetween.
On a surface of the front glass substrate 102 on the side of the discharge space 111, n strip-like electrodes 104a and n strip-like electrodes 105a which are paired respectively are extendedly formed. For convenience of illustration range, one electrode 104a and one electrode 105a are shown in FIG. 17. The electrodes 104a and 105a which are paired with each other are arranged with a discharge gap DG interposed therebetween. The electrodes 104a and 105a work to induce a discharge. Further, a transparent electrode is used for the electrodes 104a and 105a to extract more visible light, and hereinafter the electrodes 104a and 105a are also referred to as transparent electrodes 104a and 105a. Furthermore, in some cases, the electrodes 104a and 105a are made of the same material as metal (auxiliary) electrodes (or bus electrodes) 104b and 105b as discussed later are made of On the transparent electrodes 104a and 105a, the metal (auxiliary) electrodes (or bus electrodes) 104b and 105b are formed extendedly along the transparent electrodes 104a and 105a. The metal electrodes 104b and 105b have impedance lower than those of the transparent electrodes 104a and 105a, and work to supply a current from a driving device.
In the following discussion, an electrode constituted of the transparent electrode 104a and the metal electrode 104b is referred to as a (row) electrode 104 (or X) and an electrode constituted of the transparent electrode 105a and the metal electrode 105b is referred to as a (row) electrode 105 (or Y). The row electrodes 104 and 105 (or row electrodes X and Y) which are paired with each other are also referred to as a pair of (row) electrodes 104 and 105 (or a pair of (row) electrodes X and Y). Further, in some cases, the row electrode 104 is constituted of only electrode which corresponds to the electrode 104a and/or the row electrode 105 is constituted of only electrode which corresponds to the electrode 105a. 
A dielectric layer 106 is formed covering the row electrodes 104 and 105 and a protection film 107 made of MgO (magnesium oxide) which is a dielectric substance is formed on a surface of the dielectric layer 106 by evaporation method and the like. The dielectric layer 106 and the protection film 107 are also generally referred to as a dielectric layer 106A. Further, in some cases, the dielectric layer 106A does not include the protection film 107.
On the other hand, on a surface of the rear glass substrate 103 on the side of the discharge space 111, m strip-like (column) electrodes 108 are so formed extendedly as to be orthogonal to (as to grade-separately intersect) the row electrodes 104 and 105. Hereinafter, the (column) electrode 108 is also referred to as a (column) electrode W Furthermore, for convenience of illustration range, three electrodes 108 are shown in FIG. 17.
Between the adjacent column electrodes 108, a barrier rib 110 is formed extendedly in parallel with the column electrodes 108. The barrier ribs 110 separate a plurality of discharge cells (discussed later) arranged along the extending direction of the row electrodes 104 and 105 from each other and the barrier ribs 110 support the PDP 101 so as not to be crushed by atmospheric pressure.
Inside a substantial U-shaped trench constituted of the adjacent barrier ribs 110 and the rear glass substrate 103, a phosphor layer 109 is formed covering the column electrode 108. In more detail, in the above substantial U-shaped trenches, phosphor layers 109R, 109G and 109B for respective emitted light colors, red, green and blue are formed and for example, the phosphor layers 109R, 109G and 109B are arranged in this order in the entire PDP 101.
The front glass substrate 102 and the rear glass substrate 103 having the above structure are sealed with each other and the discharge space 111 between the front glass substrate 102 and the rear glass substrate 103 is filled with discharge gas such as Nexe2x80x94Xe mixed gas or the Hexe2x80x94Xe mixed gas under a pressure lower than the atmospheric pressure.
In the PDP 101, a discharge cell or a light emitting cell is formed at a (grade-separation) intersection of the row electrodes 104 and 105 and the column electrode 108. Specifically, three discharge cells are shown in FIG. 17.
(Principle of Operation of PDP)
Next, a principle of display operation of the PDP 101 will be discussed. First, a voltage or a voltage pulse is applied across the row electrodes 104 and 105 to generate a discharge in the discharge space 111. Then, by exciting the phosphor layer 109 with an ultraviolet ray generated by this discharge, the discharge cell emits light or lights up. Charged particles such as electrons and ions generated in the discharge space 111 through this discharge move in a direction of the row electrode to which a voltage having a polarity reverse to that of the charged particles is applied and are accumulated on the surface of the dielectric layer 106A on the row electrode (referred to as xe2x80x9con the row electrodexe2x80x9d hereinafter). The electric charges such as electrons and ions accumulated on the surface of the dielectric layer 106A are referred to as xe2x80x9cwall charges.xe2x80x9d
Since the respective wall charges accumulated on the row electrodes 104 and 105 through the discharge form an electric field in a direction of weakening the electric field between the pair of the row electrodes 104 and 105, the discharge quickly disappears with formation and accumulation of the wall charges. When a voltage having polarity reverse to that of the above voltage is applied to the row electrodes 104 and 105 after the discharge disappears, an electric field in which the electric field generated by the applied voltage is superimposed on the electric field generated by the wall charges is substantially applied to the discharge space 111, i.e., a voltage in which the applied voltage is superimposed on the voltage (wall voltage) generated by the wall charges is substantially applied to the discharge space 111. The superimposed electric field can cause a discharge again.
Specifically, once the discharge is generated, continuous discharge (sustain discharge) can be caused by a voltage (sustain voltage) lower than the applied voltage used for starting the initial discharge through the electric field generated by the wall charges. Therefore, after the discharge is once generated, by alternately applying a pulse (sustain pulse) having an amplitude of sustain voltage to the row electrodes 104 and 105, in other words, by applying the sustain pulse across the row electrodes 104 and 105 with its polarity reversed, the discharge can be regularly sustained and continued (sustain operation).
Specifically, the discharge can be continued by continuously applying the sustain pulse until the wall charges disappear. Further, to extinguish the wall charges is referred to as xe2x80x9can erase operationxe2x80x9d (or simply as xe2x80x9can erasexe2x80x9d) while to form the wall charges on the dielectric layer 106A at the start of continuous discharge (sustain discharge) is referred to as xe2x80x9ca writing operationxe2x80x9d (or simply as xe2x80x9ca writingxe2x80x9d).
An actual image display is repeated with one field set within 16.6 ms, considering the human visual characteristics. At this time, in general, one field is divided into a plurality of subfields and the subfields have different luminances to make a gradation or tone. One subfield includes a reset period, an addressing period and a sustain period.
In the reset period, discharge (priming discharge) is generated in all the cells regardless of display history in order to enhance the discharge probability. Concurrently with this discharge, the wall charges are erased to erase the display history.
In the addressing period, a discharge cell is selected in matrix by combination of the row electrode 104 (105) and the column electrode 108 to generate a discharge (writing discharge or addressing discharge) in the predetermined discharge cell(s).
In the sustain period, discharges are repeatedly generated a predetermined number of times in the discharge cell(s) in which the writing discharge is generated in the addressing period. The luminance depends on the number of repeating generations of discharges.
In a predetermined discharge cell (or a plurality of predetermined discharge cells) among a plurality of discharge cells arranged in matrix, the writing discharge is first generated and then the sustain discharge is generated, to display characters, figures, images and the like. Further, by quickly performing the writing operation, the sustain operation and the erase operation, a movie display can be also performed.
(Power Recovery Circuit)
The PDP 101, which has the above structure, forms a capacitive load having floating capacitance among the row electrodes 104 and 105 and the column electrode 108. Therefore, a current flows in a capacitance element of the PDP 101 every time when the voltage is applied. The power of this time is not concerned in the display and therefore referred to as a reactive power. Next, a power recovery circuit (hereinafter, referred to simply as a recovery circuit) for recovering and recycling such a reactive power will be discussed. In the sustain period, generally, the sustain pulse of about 40 kHz is applied to the PDP. Since the reactive power largely depends on the frequency of the sustain pulses, the recovery circuit is used to recover the reactive power generated in the operation during the sustain period.
FIG. 18 is a circuit diagram showing a recovery circuit in the background art. This is disclosed in e.g., Japanese Patent Application Laid Open Gazette Nos. 63-101897 and 62-192798. In FIG. 18, the PDP 101 is schematically represented as capacitance element CP. Herein, discussion will be made on a case where a voltage pulse is applied to an electrode (which corresponds to the electrode X) on the left side of the capacitance element CP as one faces the figure.
The rise of the voltage pulse is performed as follows. First, a switch 312 of a recovery circuit 302 is turned on to move the electric charges accumulated in a capacitor 310 to the capacitance element CP through a reactor 308. This carries a current. After that, at a proper timing, a switch 304 is turned on to apply a voltage (sustain pulse) Vs of a main power supply to the electrode on the left side of the capacitance element CP.
On the other hand, the fall of the voltage pulse is performed as follows. First, the switches 304 and 312 are turned off and a switch 313 is turned on. The electric charges are thereby moved from the capacitance element CP to the recovery capacitor 310 through the reactor 308 and the switch 313 and the electric charges are accumulated in the recovery capacitor 310. After that, a switch 305 is turned on to bring the electrode on the left side of the capacitance element CP into a ground potential (GND), and the voltage pulse thereby falls.
This operation, only to move the electric charges between the capacitance element CP and the recovery capacitor 310, loses the reactive power. Further, moving the electric charges between an electrode (which corresponds to the electrode Y) on the right side of the capacitance element CP and the recovery capacitor 311 can be performed in the same manner.
(Driving Method Using Round Pulse)
In general, as a sustain pulse used is a rectangular waveform or a rectangular pulse having a sharp rise, in other words, a rectangular pulse which rises fast. The rectangular pulse is used in order to generate an intense discharge by the sustain pulse and thereby generate a sufficient amount of wall charges. In more detail, in a case of using the rectangular pulse which rises sufficiently fast, the discharge starts after the rectangular pulse reaches a final attainment potential (or final attainment voltage; hereinafter, also referred to simply as a final potential (or final voltage)). Specifically, from the time when the applied voltage exceeds a firing voltage until the discharge is actually generated, there is a time lag called a discharge delay time. The applied rectangular pulse reaches the final potential before the discharge delay time passes. Therefore, since a sufficient high voltage is applied to the discharge space, a lot of wall charges are generated and accumulated.
In contrast to this, as the priming discharge and the like, a pulse of round waveform, i.e., a round pulse is used, in some cases. Since it is desirable that a discharge not for display luminescence, such as the priming discharge, is weak in terms of contrast, the round pulse which can generate a relatively weak discharge is used. Further, also when the wall charges are erased, a predetermined amount of wall charges are generated or the like, the round pulse is sometimes used.
When the rise time (and/or fall time) of the round pulse is longer than the discharge delay time and the round pulse rises (falls) sufficiently slow, a very weak discharge starts at the minimum voltage value. In the case of this discharge, the amount of movement of wall charges is very small and the discharge continues all the while the voltage continues to change after the discharge starts. In more detail, the discharge is once generated near the firing voltage to generate a very small amount of wall charges. Since the voltage across electrodes exceeds the firing voltage again with the continuous rise of the applied voltage, the discharge is generated again. By repeating generations of such a very small discharge, a weak discharge continues all the while the applied voltage continues to change. At this time, a predetermined amount of wall charges which depend on the final potential of the round pulse are stably generated. Furthermore, it is possible to extinguish the wall charges, depending on the application polarity and the final potential of the round pulse.
The round pulse mainly includes two types of pulses, i.e., a xe2x80x9cCR waveform (or CR pulse)xe2x80x9d and a xe2x80x9cramp waveform (or ramp pulse)xe2x80x9d (see a CR pulse 20 and a ramp pulse 10 of FIG. 19). These waveforms will be discussed below.
The CR pulse is obtained when a capacitance element is charged (or discharged) through a resistance element. When a capacitance element C having a voltage of 0 in an initial state is charged by a power supply having a voltage V0 ( greater than 0) through a resistance element R, a voltage of the capacitance element C, i.e., a voltage v(t) of the CR pulse is expressed as
v(t)=V0xc3x97(1xe2x88x92exp(xe2x88x92t/xcfx84))
where t represents time and xcfx84 is a time constant expressed by a product of the capacitance element C and the resistance element R (xcfx84=Cxc3x97R). Since the voltage v(t) includes a term of exponential function, the waveform of the voltage v(t) is sometimes termed xe2x80x9can exponential waveformxe2x80x9d.
The rate of change dv(t)/dt (hereinafter, also referred to as xe2x80x9cdv/dtxe2x80x9d) of the voltage v(t) with respect to time t is obtained as
dv(t)/dt=(V0/xcfx84)xc3x97exp(xe2x88x92t/xcfx84)
It can be seen from this equation that the rate of voltage change dv(t)/dt of the CR pulse is large immediately after the application and gradually becomes smaller with time. Since the PDP is a capacitive load, as discussed earlier, the CR pulse can be applied to the electrode of the PDP or the capacitance element only by supplying the voltage to the electrode through a resistance.
On the other hand, the voltage v(t) of the ramp pulse is in proportion to an application time t, and in other words, it increases (or decreases) at a constant rate of voltage change dv/dt. With the ramp pulse, unlike with the CR pulse, the discharge can be started always at a constant rate of voltage change, not depending on variation in firing voltage. Therefore, it is possible to absorb variation in discharge characteristics of the discharge cells and suppress variation in light emission all over the PDP.
The CR pulse and the ramp pulse, however, have the following problems.
(Problem of CR Pulse)
When a discharge is started with a relatively low voltage by using the CR pulse, there is a problem of a long application time of the pulse.
As discussed above, the rate of voltage change dv/dt is large immediately after the CR pulse is applied, and in such a time region where the rate of voltage change is large, an intense discharge is generated, like with the rectangular pulse. Further, even with the ramp pulse, if the rate of voltage change dv/dt is large, such an intense discharge is generated.
This is because when the rate of voltage change dv/dt is large, the voltage v(t) of the round pulse (including the CR pulse and the ramp pulse) reaches a high voltage after it exceeds the firing voltage before the discharge delay time passes, like in the case of the rectangular pulse. When the intense discharge is generated, a lot of wall charges are generated and accumulated. Since the wall charges have a polarity to suppress (weaken) the externally-applied voltage, once a lot of wall charges are accumulated, the voltage does not exceed the firing voltage again even with the continuous increase of the voltage of the round pulse. As a result, the discharge is intermitted and the characteristic feature of the round pulse can not be obtained. Specifically, the above-discussed continuous weak discharge can not be obtained and it is therefore impossible to stably obtain a predetermined amount of wall charges which depend on the final potential of the round pulse.
In order to obtain the characteristic feature of the round pulse, it is necessary to sufficiently lower the rate of voltage change dv/dt at the start of discharge, and specifically, it is necessary to sufficiently increase the time constant xcfx84 in the case of the CR pulse. When the rate of voltage change dv/dt is lowered, however, the time period until the round pulse completely rises, i.e., the application time of the pulse becomes longer. In the case of the CR pulse, particularly, since the rate of voltage change dv/dt becomes smaller as the time passes from the application of the pulse, it takes very long for the voltage to approximate the final voltage.
Additionally, when there is variation in firing voltage of the discharge cells, when the discharge is started in all the discharge cells with a small rate of voltage change dv/dt, there arises a necessity to further increase the time constant. In contrast to this, with the ramp pulse, as discussed above, it is possible to start the discharge always at a constant rate of voltage change, not depending on the variation in firing voltage.
(Problem of Ramp Pulse)
When the discharge is started with a high applied voltage because of a small amount of wall charges, the polarity of the wall charges reverse to that of the round waveform or the like, however, it sometimes becomes necessary to apply the ramp pulse for a long time. This will be discussed with reference to FIG. 19.
In FIG. 19, the ramp pulse 10 and the CR pulse 20 are staggered so that the respective rate of voltage changes dv/dt of the ramp pulse 10 and the CR pulse 20 at the firing voltage Vf may be equal to each other. In other words, the tangent of the CR pulse 20 at the firing voltage Vf corresponds to the ramp pulse 10. Further, it is assumed that the rate of voltage change dv/dt or the inclination of waveform of the ramp pulse 10 keeps to such a minimum as to generate a very weak discharge in the discharge cell having the firing voltage Vf.
At this time, as can be seen from FIG. 19, a time period T10gf from the time when the ramp pulse 10 rises to the time when it reaches the firing voltage Vf is longer than a time period T20gf from the time when the CR pulse 20 rises to the time when it reaches the firing voltage Vf. Further, a time period T10fr from the time when the ramp pulse 10 is at the firing voltage Vf to the time when it reaches the final voltage Vr is shorter than a time period T20fr from the time when the CR pulse 20 is at the firing voltage Vf to the time when it reaches the final voltage Vr. Furthermore, the relation between the sum of the time periods T10gf and T10fr and the sum of the time periods T20gf and T20fr depends on the relation between the firing voltage Vf and the rate of voltage change dv/dt needed at the start of discharge.
Thus, with the round pulse which has the rate of voltage change dv/dt giving the above characteristic feature, a very long application time is needed.
(Problem in Method of Driving Using Round Pulse)
An driving operation in one driving cycle of the PDP has to be completed within one field period (about 16 ms in the case of NTSC-TV signal) of an image input signal. If the driving operation is not completed within one field period, there arise problems of not-synchronization between a signal input and a display image and the like.
Since the application time of the round pulse is very long as discussed above, there may occur a case where the driving operation can not be completed within one field period in a driving method using the round pulse. Therefore, in a case of using the round pulse, it is necessary to, for example, reduce the number of subfields or narrow the width of a pulse other than the round pulse such as the applied pulse in the addressing period (address pulse) and the sustain pulse.
Reducing the number of subfields, however, causes deterioration of display quality such as decrease in the number of tones. Further, narrowing the width of the address pulse, the sustain pulse and the like makes the discharge unstable and as a result, a driving voltage margin decreases to make the operation unstable. Therefore, when the round pulse is used, it is desirable to reduce the needed time.
One of techniques to reduce the application time of the round pulse is disclosed in Japanese Patent Application Laid Open Gazette No. 6-314078. This technique will be discussed with reference to FIGS. 20 and 21. As shown in FIG. 20, in a round pulse generation circuit 401 disclosed in the laid open gazette, a Zener diode 403 is connected in parallel to a resistor 402. In the round pulse generation circuit 401, it is possible to apply a voltage which sharply changes at an initial time of pulse application and then gently changes (at low rate of voltage change), such as a voltage pulse 410 shown in FIG. 21.
For example, if the discharge starts in a region where the voltage changes sharply when there is very large variation in firing voltage or the firing voltage is lowered with time-varying change, however, the above-discussed intense discharge is generated even with the pulse 410 and the characteristic feature of the round pulse can not be obtained.
Further, the round pulse generation circuit 401 has problems of large circuit scale and high cost. This will be discussed below. When the voltage sharply changes, a very large current flows in the Zener diode 403 and a voltage over a Zener voltage Vz is applied thereto. Therefore, there occurs a very large power loss in the Zener diode 403. Further, since the Zener voltage Vz itself is a voltage equivalent to the firing voltage, it is necessary to use a diode of high breakdown voltage as the Zener diode 403. Thus, since the Zener diode 403 needs a high breakdown and a large permissible loss, the round pulse generation circuit 401 is large in circuit scale and needs high cost.
(1) The present invention is directed to a method of driving a plasma display panel which comprises a discharge cell including a first electrode and a second electrode, capable of controlling generation/non-generation of discharge with potential difference between the first electrode and the second electrode. According to a first aspect of the present invention, the method of driving a plasma display panel comprises: a pulse applying step of applying a voltage pulse which continuously changes from a first voltage to a second voltage to the first electrode, and in the method of the first aspect, the pulse applying step comprises the steps of: (a) generating a first region of the voltage pulse by a first pulse generation system and applying the same; and (b) generating a second region of the voltage pulse different from the first region by a second pulse generation system different from the first pulse generation system and applying the same.
(2) According to a second aspect of the present invention, in the method of the first aspect, a voltage change in the first region is gentler than that in the second region.
(3) According to a third aspect of the present invention, in the method of the second aspect, the step (a) is performed after the step (b).
(4) According to a fourth aspect of the present invention, in the method of any one of the first to third aspects, the pulse applying step further comprises the step of: (c) generating a third region of the voltage pulse different from the first and second regions by a third pulse generation system different from the first pulse generation system and applying the same.
(5) According to a fifth aspect of the present invention, in the method of any one of the first to fourth aspects, the voltage pulse includes part of one of a CR voltage pulse, a ramp voltage pulse and an LC resonant voltage pulse.
(6) According to a sixth aspect of the present invention, in the method of any one of the first to fifth aspects, the voltage pulse is generated by utilizing a reactive power generated in driving the plasma display panel in the pulse applying step.
(7) According to a seventh aspect of the present invention, in the method of driving a plasma display panel which comprises a discharge cell including a first electrode and a second electrode, capable of controlling generation/non-generation of discharge with potential difference between the first electrode and the second electrode, a voltage pulse which continuously changes from a first voltage to a second voltage and changes more sharply as it approaches the second voltage is applied to the first electrode.
(8) The present invention is also directed to a plasma. display device. According to an eighth aspect of the present invention, the plasma display device comprises a plasma display panel comprising a discharge cell including a first electrode and a second electrode; and a driving unit for driving the discharge cell by giving a potential difference between the first electrode and the second electrode, and in the plasma display device of the eighth aspect, the driving unit comprises a pulse generation unit capable of generating a voltage pulse by using a first pulse generation system and a second pulse generation system, and the driving unit generates the voltage pulse including a first region generated by the first pulse generation system and a second region being different from the first region, generated by the second pulse generation system and continuously changing from a first voltage to a second voltage, to output the voltage pulse as a voltage to be applied to the first electrode.
(9) According to a ninth aspect of the present invention, in the plasma display device of the eighth aspect, a voltage change in the first region is gentler than that in the second region.
(10) According to a tenth aspect of the present invention, in the plasma display device of the ninth aspect, the driving unit generates the first region before the second region.
(11) According to an eleventh aspect of the present invention, in the plasma display device of any one of the eighth to tenth aspects, the pulse generation unit generates the voltage pulse by further using a third pulse generation system different from the first pulse generation system, and the driving unit generates the first region between the second region and a third region different from the first and second regions, the third region is generated by the third pulse generation system.
(12) According to a twelfth aspect of the present invention, in the plasma display device of any one of the eighth to eleventh aspects, the voltage pulse includes part of one of a CR voltage pulse, a ramp voltage pulse and an LC resonant voltage pulse.
(13) According to a thirteenth aspect of the present invention, in the plasma display device of any one of the eighth to twelfth aspects, the driving unit further comprises a power recovery unit, and the driving unit generates the voltage pulse by utilizing a reactive power recovered in the power recovery unit.
(14) According to a fourteenth aspect of the present invention, the plasma display device comprises a plasma display panel comprising a discharge cell including a first electrode and a second electrode; and a driving unit for driving the discharge cell by giving a potential difference between the first electrode and the second electrode, and in the plasma display device of the fourteenth aspect, the driving unit generates a voltage pulse which continuously changes from a first voltage to a second voltage and changes more sharply as it approaches the second voltage, to output the voltage pulse as a voltage to be applied to the first electrode.
(15) The present invention is further directed to a driving device for a plasma display panel, the plasma display panel comprising a discharge cell including a first electrode and a second electrode. According to a fifteenth aspect of the present invention, the driving device for a plasma display panel comprises the driving unit as defined in any one of the eighth to fourteenth aspects.
(1) By the method of the first aspect of the present invention, the first region and the second region of the voltage pulse can be controlled and set independently of each other. Therefore, it is possible to reduce the application time of the voltage pulse as compared with the case of generating and applying the voltage pulse only by a single pulse generation system.
(2) By the method of the second aspect of the present invention, the voltage change in the first region is gentler than that of the second region. In other words, the voltage change in the second region is sharper than that in the first region. Therefore, it is possible to reduce the application time of the voltage pulse as compared with the case of generating and applying the voltage pulse only by the first pulse generation system. This effect can be obtained regardless of whether the first region or the second region is precedent to the other.
In this case, when a discharge is generated in the first region, the discharge is weaker than that generated in the second region. Further, with a sufficiently gentle voltage change in the first region, a continuous very weak discharge can be generated, and as a result, an effect caused by such a continuous very weak discharge, e.g., of stably generating a constant amount of wall charges which depend on the voltage at the end of application of the voltage pulse can be produced.
(3) By the method of the third aspect of the present invention, the second region in which the voltage pulse is sharper than that in the first region is provided before the first region. In this case, by making the voltage pulse in the second region gentler, even if the discharge is started in the second region, the above continuous very weak discharge can be generated in the subsequent first region.
(4) By the method of the fourth aspect of the present invention, with the voltage pulse in the third region sharper than that in the first region, it is possible to reduce the application time as compared with the method of the first aspect.
(5) The method of the fifth aspect of the present invention can produce the same effect as any one of the methods of the first to fourth aspects produces.
(6) The method of the sixth aspect of the present invention can produce the same effect as any one of the methods of the first to fifth aspects produces and allows reduction in reactive power which is not concerned in the display.
(7) By the method of the seventh aspect of the present invention, it is possible to reduce the application time of the voltage pulse as compared with that of e.g., the ramp voltage pulse.
In this case, when a discharged is generated in a region near the first voltage where the voltage change is gentle, a discharge weaker than that in a region where the voltage change is sharp can be achieved. Further, with a sufficiently gentle voltage change in the region where the voltage change is gentle, a continuous very weak discharge can be generated, and as a result, an effect caused by such a continuous very weak discharge, e.g., of stably generating a constant amount of wall charges which depend on the voltage at the end of application of the voltage pulse can be produced.
(8) The plasma display device of the eighth aspect of the present invention can produce the same effect as the method of the first aspect produces.
(9) The plasma display device of the ninth aspect of the present invention can produce the same effect as the method of the second aspect produces.
(10) The plasma display device of the tenth aspect of the present invention can produce the same effect as the method of the third aspect produces.
(11) The plasma display device of the eleventh aspect of the present invention can produce the same effect as the method of the fourth aspect produces.
(12) The plasma display device of the twelfth aspect of the present invention can produce the same effect as the method of the fifth aspect produces.
(13) The plasma display device of the thirteenth aspect of the present invention can produce the same effect as the method of the sixth aspect produces.
(14) The plasma display device of the fourteenth aspect of the present invention can produce the same effect as the method of the seventh aspect produces.
(15) By the driving device of the fifteenth aspect of the present invention, it is possible to provide a driving device for a plasma display panel which can produce any one of the effects of the eighth to fourteenth aspects.
A first object of the present invention is to provide a method of driving a plasma display panel, which allows reduction in application time as compared with a case of applying, e.g., the CR pulse.
A second object of the present invention is to provide a method of driving a plasma display panel, which produces an effect of stably generating a constant amount of wall charges which depend on, e.g., the final voltage by the round pulse, as well as achieves the first object.
A third object of the present invention is to provide a method of driving a plasma display panel, which allows reduction in reactive power, as well as achieves the first and second objects.
A fourth object of the present invention is to provide a plasma display device and a driver for a plasma display panel, which can achieve the first to third objects.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.